The problem with a 0% return is how destructive inflation is to value of the original investment over a long period of time. This is not something that should give anybody any comfort.
As an example, in 1970 my parents bought a house in suburban Washington DC (Fairfax County, VA) for $50,000. In 2003, they sold it for $505,000 in a peak inflated sellers market. This sounds excellent, but over 33 years only represents about 7% growth, about 2% of which was due to the major uptick in housing prices in the 2 years right before sale. But the value of that asset didn’t come from saving anything - 90% of it came from appreciation of the asset, which has nothing to do with buying the original equity.
In practical terms, the original “forced savings” of $50K in 1970 dollars had been devalued from a suburban family home to a reasonably nice car. This is the “money under the mattress” problem - cash loses value day by day as inflation raises prices.
Had they been able to pay interest only over that time and invested the difference at an 8% return, they would have had a second asset worth ~$770K - more than the house itself, because over time houses generally appreciate at the rate of inflation, except when there are financial sector driven housing bubbles.
I suspect all of us would be much more comfortable with the liquid asset of $770K over the $50K of 1970 equity still tied up in a house and unavailable to us except by taking out a loan against our own money.
Now having said this, I am carrying a 40 year fixed at 3%. As is said, “People don’t buy house price, they buy payments.” I can’t reasonably buy a lower payment than what I am paying, so it would be foolish to attempt to do so and pay interest only taking the risk of rate adjustments.
Anyway, people think of houses as assets, but assets pay you and that is the opposite of what a house does, at least to the extent you are living in it.
The asset for a house is the mortgage on the bank’s balance sheet. It’s a liability on our balance sheet that we can aspire to own outright, although I would keep a first position lien on a house of some moderate value as that is protective in the event you are ever sued against your personal assets since there is already a first position lien holder with collateral rights, and that lienholder has no rights against you so long as you make your payments.
I’m not saying there is all that much any of us can do about any of this - it’s investment and risk strategy that most people aren’t willing to manage against the emotions of “home”. Same reason many buy over leasing even though it may not make financial sense, especially with changes in the tax laws.